The present invention relates to new N-acylamino aryl derivatives, to processes and intermediates for their preparation, and to pharmaceutical compositions containing them. These compounds are selective monoamine oxidase inhibitors and, therefore, are useful for treating or preventing diseases mediated by monoamine oxidase B.
Monoamine oxidase (MAO, EC 1.4.3.4) is a flavin-containing enzyme responsible for the oxidative deamination of endogenous monoamine neurotransmitters such as dopamine, serotonin, adrenaline, or noradrenaline, and trace amines, e.g. phenylethyl-amine, as well as a number of amine xenobiotics. The enzyme exists in two forms, MAO-A and MAO-B, encoded by different genes (A. W. Bach et al., Proc. Natl. Acad. Sci. USA 1988, 85, 4934-4938) and differing in tissue distribution, structure and substrate specificity. MAO-A has higher affinity for serotonin, octopamine, adrenaline, and noradrenaline; whereas the natural substrates for MAO-B are phenylethylamine and tyramine. Dopamine is thought to be oxidised by both isoforms. MAO-B is widely distributed in several organs including brain (A. M. Cesura and A. Pletscher, Prog. Drug Research 1992, 38, 171-297). Brain MAO-B activity appears to increase with age. This increase has been attributed to the gliosis associated with aging (C. J. Fowler et al., J. Neural. Transm. 1980, 49, 1-20). Additionally, MAO-B activity is significantly higher in the brains of patients with Alzheimer""s disease (P. Dostert et al., Biochem. Pharmacol. 1989, 38, 555-561) and it has been found to be highly expressed in astrocytes around senile plaques (Saura et al., Neuroscience 1994, 70, 755-774). In this context, since oxidative deamination of primary monoamines by MAO produces NH3, aldehydes and H2O2, agents with established or potential toxicity, it is suggested that there is a rationale for the use of selective MAO-B inhibitors for the treatment of dementia and Parkinson""s disease. Inhibition of MAO-B causes a reduction in the enzymatic inactivation of dopamine and thus prolongation of the availability of the neurotransmitter in dopaminergic neurons. The degeneration processes associated with age and Alzheimer""s and Parkinson""s diseases may also be attributed to oxidative stress due to increased MAO activity and consequent increased formation of H2O2 by MAO-B. Therefore, MAO-B inhibitors may act by both reducing the formation of oxygen radicals and elevating the levels of monoamines in the brain.
Given the implication of MAO-B in the neurological disorders mentioned above, there is considerable interest to obtain potent and selective inhibitors that would permit control over this enzymatic activity. The pharmacology of some known MAO-B inhibitors is for example discussed by D. Bentuxc3xa9-Ferrer et al. in CNS Drugs 1996, 6, 217-236. Whereas a major limitation of irreversible and non-selective MAO inhibitor activity is the need to observe dietary precautions due to the risk of inducing a hypertensive crisis when dietary tyramine is ingested, as well as the potential for interactions with other medications (D. M. Gardner et al., J. Clin. Psychiatry 1996, 57, 99-104), these adverse events are of less concern with reversible and selective MAO inhibitors, in particular of MAO-B. Thus, there is a need for MAO-B inhibitors with a high selectivity and without the adverse side-effects typical of irreversible MAO inhibitors with low selectivity for the enzyme.
It is an object of the present invention to provide compounds having the following formula 
in which X is xe2x80x94CHRO, xe2x80x94OCHRxe2x80x94, xe2x80x94CH2Sxe2x80x94, xe2x80x94SCH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or xe2x80x94Cxe2x89xa1Cxe2x80x94, and the other variables are defined herein. The invention also provides for pharmaceutically acceptable salts of these compounds.
It has been found that the compounds of the invention are highly selective MAO-B inhibitors. Therefore, it is another object of the invention to provide compositions containing one or more compounds of formula I and a pharmaceutically acceptable carrier. It a further object of the invention to provide methods for the treatment or prevention of diseases mediated by monoamine oxidase B inhibitors. It is also an object of the present invention to provide a process for the manufacture of compounds of the invention, for example, compounds of formula I.
The following definitions of general terms used in the present patent application apply irrespective of whether the terms in question appear alone or in combination. It must be noted that, as used in the specification and the appended claims, the singular forms xe2x80x9caxe2x80x9d, xe2x80x9can,xe2x80x9d and xe2x80x9cthexe2x80x9d include plural forms unless the context clearly dictates otherwise.
The term xe2x80x9c(C1-C6)-alkylxe2x80x9d (xe2x80x9clower alkylxe2x80x9d) used in the present application denotes straight-chain or branched saturated hydrocarbon residues with 1 to 6 carbon atoms, preferably with 1 to 3 carbon atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, t-butyl, and the like. Accordingly, the term xe2x80x9c(C1-C3)-alkylxe2x80x9d means a straight-chain or branched saturated hydrocarbon residue with 1 to 3 carbon atoms.
The term xe2x80x9chalogenxe2x80x9d denotes fluorine, chlorine, bromine and iodine.
xe2x80x9cHalogen-(C1-C6)-alkylxe2x80x9d or xe2x80x9chalogen-(C1-C6)-alkoxyxe2x80x9d means the lower alkyl residue or lower alkoxy residue, respectively, as defined herein substituted in any position with one or more halogen atoms as defined herein. Examples of halogenalkyl residues include, but are not limited to, 1,2-difluoropropyl, 1,2-dichloropropyl, trifluoromethyl, 2,2,2-trifluoroethyl, 2,2,2-trichloroethyl, and 1,1,1-trifluoropropyl, and the like. xe2x80x9c
Halogenalkoxyxe2x80x9d includes trifluoromethyloxy.
xe2x80x9c(C1-C6)-Alkoxyxe2x80x9d means the residue xe2x80x94Oxe2x80x94R, wherein R is a lower alkyl residue as defined herein. Examples of alkoxy radicals include, but are not limited to, methoxy, ethoxy, isopropoxy, and the like.
The term xe2x80x9c(C3-C7)-cycloalkylxe2x80x9d denotes a saturated carbocyclic group, containing 3 to 7 carbon atoms. For example, a cycloalkyl group is cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl, and these groups may optionally be substituted by one or two (C1-C4)-alkyl substituents, for example methyl or ethyl.
xe2x80x9cPharmaceutically acceptable,xe2x80x9d such as pharmaceutically acceptable carrier, excipient, etc., means pharmacologically acceptable and substantially non-toxic to the subject to which the particular compound is administered.
xe2x80x9cPharmaceutically acceptable saltsxe2x80x9d of a compound means salts that are pharmaceutically acceptable, which are generally safe, non-toxic, and neither biologically nor otherwise undesirable, and that possess the desired pharmacological activity of the parent compound. These salts are derived from an inorganic or organic acid or base. If possible, compounds of formula I may be converted into pharmaceutically salts. It should be understood that pharmaceutically acceptable salts are included in the present invention.
xe2x80x9cTherapeutically effective amountxe2x80x9d means an amount that is effective to prevent, alleviate or ameliorate symptoms of disease or prolong the survival of the subject being treated.
It is an object of the present invention to provide compounds having the following formula 
wherein
R1 is halogen, halogen-(C1-C6)-alkyl, cyano, (C1-C6)-alkoxy or halogen-(C1-C6)-alkoxy;
R21, R22, R23 and R24 are each independently selected from the group consisting of hydrogen, (C1-C6)-alkyl, halogen, halogen-(C1-C6)-alkyl, hydroxy, (C1-C6)-alkoxy and xe2x80x94CHO;
R3 is hydrogen or (C1-C3)-alkyl;
R4, R5 are each independently selected from the group consisting of hydrogen, (C1-C6)-alkyl, (C1-C6)-alkoxy or xe2x80x94COO(C1-C6)alkyl;
or, alternatively, R4 and R5, together with the C-atom to which they are attached, form a (C3-C7)-cycloalkyl ring;
R6 is xe2x80x94COxe2x80x94NR7R8; xe2x80x94COO(C1-C6)-alkyl, xe2x80x94CN, xe2x80x94N(R)2 or xe2x80x94NHC(O)R;
R7 and R8 are each independently selected from the group consisting of hydrogen,
(C1-C6)-alkyl, NH2 or hydroxy;
R is hydrogen or (C1-C6)-alkyl;
n is 0, 1, 2 or 3;
X is xe2x80x94CHRO, xe2x80x94OCHRxe2x80x94, xe2x80x94CH2Sxe2x80x94, xe2x80x94SCH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or xe2x80x94Cxe2x89xa1Cxe2x80x94;
or the pharmaceutically acceptable salts thereof.
Among compounds of the present invention certain compounds of formula I are preferred, for example the compounds of formula Ia below are preferred embodiments: 
wherein
R1 is halogen, halogen-(C1-C6)-alkyl, cyano, (C1-C6)-alkoxy or halogen-(C1-C6)-alkoxy;
R21, R22, R23 and R24 are each independently selected from the group consisting of hydrogen and halogen;
R3 is hydrogen or (C1-C3)-alkyl;
R4 is hydrogen or (C1-C6)-alkyl;
R5 is hydrogen or (C1-C6)-alkyl;
or, alternatively, R4 and R5, together with the carbon atom to which they are attached, form a (C3-C7)-cycloalkyl ring;
R6 is xe2x80x94COxe2x80x94NR7R8, xe2x80x94COO(C1-C6)-alkyl, or xe2x80x94CN;
R7 and R8 are each independently hydrogen, methyl or ethyl; and
n is 1, 2 or 3;
or the pharmaceutically acceptable salts thereof.
In one embodiment of the invention, compounds of formula I wherein X is CH2O or OCH2 are preferred. For example, the invention provides compounds wherein X is CH2O, preferably where X is CH2O and R6 is xe2x80x94COOC(1-6)alkyl. Preferred are further those compounds of formula I, wherein X is CH2O, R1 is fluorine or trifluoromethyl and R6 is xe2x80x94COOCH3, for example the following compounds:
N-[4-(3-fluoro-benzyloxy)-phenyl]-malonamic acid methyl ester,
N-[3-fluoro-4-(3-fluoro-benzyloxy)-phenyl]-malonamic acid methyl ester,
N-[4-(4-fluoro-benzyloxy)-phenyl]-malonamic acid methyl ester,
N-[2-fluoro-4-(3-fluoro-benzyloxy)-phenyl]-malonamic acid methyl ester,
N-[4-(2,4-difluoro-benzyloxy)-phenyl]-malonamic acid methyl ester,
N-[4-(2-fluoro-benzyloxy)-phenyl]-malonamic acid methyl ester,
N-[4-(2,4,5-trifluoro-benzyloxy)-phenyl]-malonamic acid methyl ester,
N-[2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-malonamic acid methyl ester,
N-[4-(3,5-bis-trifluoromethyl-benzyloxy)-2-fluoro-phenyl]-malonamic acid methyl ester,
N-[4-(3-fluoro-benzyloxy)-3-methyl-phenyl]-malonamic acid methyl ester or
N-[3-chloro-4-(3-fluoro-benzyloxy)-phenyl]-malonamic acid methyl ester.
Further preferred are compounds of formula I, wherein X is CH2O and R6 is xe2x80x94CONH2, for example the following compounds:
cyclopropane-1,1-dicarboxylic acid amide [4-(3-fluoro-benzyloxy)-phenyl]-amide,
N-[4-(3-fluoro-benzyloxy)-phenyl]-malonamide,
N-[4-(3-fluoro-benzyloxy)-phenyl]-2-methyl-malonamide,
N-[3-fluoro-4-(3-fluoro-benzyloxy)-phenyl]-malonamide,
N-[4-(4-fluoro-benzyloxy)-phenyl]-malonamide,
N-[4-(2,4-difluoro-benzyloxy)-phenyl]-malonamide,
N-[4-(2,4,5-trifluoro-benzyloxy)-phenyl]-malonamide,
N-[4-(2-fluoro-benzyloxy)-phenyl]-malonamide,
N-(4-benzyloxy-phenyl)-malonamide,
N-[4-(4-chloro-benzyloxy)-phenyl]-malonamide,
N-[4-(3-fluoro-benzyloxy)-2-hydroxy-phenyl]-malonamide,
N-[2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-malonamide,
N-[4-(3-fluoro-benzyloxy)-3-methyl-phenyl]-malonamide,
N-[3-chloro-4-(3-fluoro-benzyloxy)-phenyl]-malonamide or
cyclopropane-1,1-dicarboxylic acid amide [2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-amide.
Preferred are compounds of formula I wherein X is xe2x80x94OCH2xe2x80x94, for example, compounds where X is xe2x80x94OCH2xe2x80x94 and R6 is xe2x80x94NHCOCH3 or xe2x80x94NHCOH. Examples of such compounds are the following:
2-Acetylamino-N-[2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-acetamide,
2-Acetylamino-N-[2-fluoro-4-(3-fluoro-benzyloxy)-phenyl]-acetamide,
N-[2-Fluoro-4-(4-fluoro-benzyloxy)-phenyl]-2-formylamino-acetamide or
N-[2-Fluoro-4-(3-fluoro-benzyloxy)-phenyl]-2-formylamino-acetamide.
Also preferred are compounds of formula I wherein X is xe2x80x94OCH2xe2x80x94 and R6 is xe2x80x94NH2.
The following compound is an example thereof:
2-amino-N-[2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-acetamide.
In another embodiment, the invention provides compounds of formula I wherein X is xe2x80x94CH2CH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, or xe2x80x94C∉Cxe2x80x94. Such compounds include those in which X is xe2x80x94CHxe2x95x90CHxe2x80x94. Another preferred group of compounds of formula I are those, wherein X is
xe2x80x94CHxe2x95x90CHxe2x80x94 and R6 is xe2x80x94COOCH3 or xe2x80x94CONH2, for example the followings:
N-{4-[2-(4-fluoro-phenyl)-vinyl]-phenyl}-malonamic acid methyl ester,
N-{4-[2-(3-fluoro-phenyl)-vinyl]-phenyl}-malonamide,
N-{4-[2-(4-fluoro-phenyl)-vinyl]-phenyl}-malonamide or
N-{4-[2-(3-fluoro-phenyl)-vinyl]-phenyl}-malonamic acid methyl ester.
In yet another emobidment, the invention provides compounds of formula I in which X is xe2x80x94CH2Sxe2x80x94 or xe2x80x94SCH2xe2x80x94. For example, such preferred compounds include those in which X is SCH2 and R6 is COOCH3 or CONH2. Examples of such compounds are the following:
N-[4-(3-fluoro-benzylsulfanyl)-phenyl]-malonamic acid methyl ester;
and N-[4-(3-fluoro-benzylsulfanyl)-phenyl]-malonamide.
In a further embodiment, the invention provides compounds of formula I in which R1 is a halogen or halogen-(C1-C6)-alkyl. Among these compounds, those having one or more fluorine or trifluoromethyl group are preferred. Also preferred are compounds in which R1 is hydrogen, methyl, or methoxy. Examples of such compounds are the following:
N-(4-benzyloxy-phenyl)-malonamide,
N-(4-benzyloxy-phenyl)-malonamic acid methyl ester; and
N-{4-[2-(4-methoxy-phenyl)-vinyl]-phenyl}-malonamic acid methyl ester; and
In one embodiment, preferred compounds of the invention further include those in which R6 is COO(C1-C6)alkyl, for example, compounds in which R6 is COOCH3. Examples of such compounds are the following:
N-[4-(3-fluoro-benzyloxy)-phenyl]-malonamic acid methyl ester;
N-[4-(3-fluoro-benzyloxy)-phenyl]-2-methyl-malonamic acid methyl ester;
N-[4-(3-fluoro-benzyloxy)-phenyl]-2-methoxy-malonamic acid methyl ester;
N-[4-(3-fluoro-benzyloxy)-phenyl]-N-methyl-malonamic acid methyl ester;
N-[4-(3-fluoro-benzyloxy)-2-trifluoromethyl-phenyl]-malonamic acid methyl ester;
N-[4-(4-trifluoromethyl-benzyloxy)-phenyl]-malonamic acid methyl ester;
N-[2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-malonamic acid ethyl ester;
N-[2-fluoro-4-(4-trifluoromethyl-benzyloxy)-phenyl]-malonamic acid methyl ester;
N-[4-(3-fluoro-benzyloxy)-3-formyl-phenyl]-malonamic acid methyl ester;
N-[4-(3-fluoro-benzyloxy)-3-methoxy-phenyl]-malonamic acid methyl ester;
N-{4-[2-(3-fluoro-phenyl)-vinyl]-phenyl}-malonamic acid methyl ester;
N-{4-[2-(4-fluoro-phenyl)-vinyl]-phenyl}-malonamic acid methyl ester;
N-(4-benzyloxy-phenyl)-malonamic acid methyl ester;
N-[4-(3-fluoro-phenoxymethyl)-phenyl]-malonamic acid methyl ester; and
N-[4-(3-fluoro-benzylsulfanyl)-phenyl]-malonamic acid methyl ester.
In another embodiment, the invention provides compounds in which R6 is CONR7R8, for example, compounds where R6 is CONH2. Examples of such compounds are the following:
cyclopropane-1,1-dicarboxylic acid amide [4-(3-fluoro-benzyloxy)-phenyl]-amide;
N-[4-(3-fluoro-benzyloxy)-phenyl]-malonamide;
N-[4-(3-fluoro-benzyloxy)-phenyl]-2-methyl-malonamide;
N-[4-(3-fluoro-benzyloxy)-phenyl]-2,2-dimethyl-malonamide;
N-[4-(4-fluoro-benzyloxy)-phenyl]-demalonamide;
N-[4-(4-trifluoromethyl-benzyloxy)-phenyl]-malonamide;
N-{4-[2-(3-fluoro-phenyl)-vinyl]-phenyl}-malonamide;
N-{4-[2-(4-fluoro-phenyl)-vinyl]-phenyl}-malonamide;
N-[2-fluoro-4-(3-fluoro-benzyloxy)-phenyl]-malonamide;
In yet another embodiment, the invention provides compounds in which R6 is NHCOR. For example, preferred compounds are those in which R6 is NHCOCH3 or NHCOH. Examples of such compounds are the following:
2-acetylamino-N-[2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-acetamide;
2-acetylamino-N-[2-fluoro-4-(3-fluoro-benzyloxy)-phenyl]-acetamide;
N-[2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-2-formylamino-acetamide;
N-[2-fluoro-4-(3-fluoro-benzyloxy)-phenyl]-2-formylamino-acetamide; and
2-amino-N-[2-fluoro-4-(4-fluoro-benzyloxy)-phenyl]-acetamide.
In a further embodiment, the invention provides compounds in which R6 is N(R)2, particularly those compounds in which R6 is NH2.
The invention also provides compounds in which R6 is CN. An example of such a compound is 2-cyano-N-[4-(3-fluoro-benzyloxy)-phenyl]-acetamide.
The compounds of the invention, such as those of formula I, can be manufactured by reacting a compound of formula 
with a compound of formula 
to obtain a compound of formula 
and, optionally, converting a compound of formula I into a pharmaceutically acceptable salt.
In accordance with the present invention, a possibility to prepare compounds of formula I is shown in scheme 1: The key intermediates A are accessible through nucleophilic substitution of aromatic nitro compounds containing p-substituted leaving groups with benzylic alcohols or thiols. P-substituted leaving groups can be for example halogens (F, Cl, Br, I), tosylates, mesylates or triflates. These substitution reactions can be conducted neat or in inert solvents like for example toluene or xylene. Preferred reaction temperatures are between 50xc2x0 and 150xc2x0 C. Alternatively, compounds A can be prepared by Williamson-ether synthesis, starting from p-nitrophenols and benzylic halides, tosylates, mesylates or triflates. Bases used can be for example alcoholates or carbonates (sodium, potassium or cesium carbonate). Preferred solvents are lower alcohols, acetonitrile or lower ketones at temperatures between 20xc2x0 C. and reflux temperature. Another approach is the Mitsunobu-coupling of benzylic alcohols with p-nitrophenols. The reaction is done as usual in inert solvents like for example diethyl ether or tetrahydrofuran, using dialkyl-azo-dicarboxylates in presence of phosphines (for example tributyl- or triphenyl-phosphine).
The key intermediates A are reduced to the amino-compounds B using catalytic hydrogenation (for example Platinum on charcoal in lower alcohols, ethyl acetate or tetrahydrofurane). An alternative is the reduction of the nitro-group by metals like iron, tin, or zinc in acidic media like diluted hydrochloric acid or acetic acid. Metals can also be replaced by metal salts (for example tin-(II)-chloride).
Intermediates B can be acylated by known methods to give the desired compounds I-A. These reactions can be done with acid chlorides and bases (for example trialkylamines, sodium carbonate or potassium carbonate, sodium hydrogen carbonate or potassium hydrogen carbonate), eventually in presence of an acylation catalyst (e.g. 1 to 10 mol % of N,N-dimethyl-4-aminopyridine) in solvents like dichloromethane, ethyl acetate or acetonitrile, preferentially at room temperature. An alternative is the well known coupling of an acid with the amine B using coupling reagents like N,Nxe2x80x2-dicyclohexylcarbodiimide (DCC), N-(3-dimethylaminopropyl)-Nxe2x80x2-ethyl-carbodiimide hydrochloride (EDC) or 1,1xe2x80x2-carbonyl-diimidazole (CDI) in solvents like dichloromethane, diethyl ether or THF, preferentially at 0 to 40xc2x0 C. Intermediates B can also primarily be monoalkylated by known methods (see for example Johnstone et al, J. Chem. Soc. (C) 1969, 2233 or Krishnamurthy et al., Tetrahedron Lett. 1982, 23, 3315) to give compounds D. These are then acylated as previously described to lead to the desired compounds I-B.
Compounds with inverted ether or thioether linkers can be obtained by similar reactions, as depicted in scheme 1a. The key-intermediates Axe2x80x2 are then further transformed into the final products by the reaction sequences already mentioned in scheme 1.
Additional functional group manipulations can be done by standard methods on the acylated compounds to obtain all compounds of formula I (for example: functionalising the malonic position by deprotonation and reaction with electrophiles). 
Alternatively, in accordance with the present invention, compounds B can also be prepared by alkylation of N-protected p-hydroxyanilines with benzylic halides or by Mitsunobu-coupling of N-protected p-hydroxyanilines with benzylic alcohols (scheme 2) by the methods described previously. Protective groups PG can be for example N-Boc (N-tert.-butoxycarbonyl) or N-acetyl. Deprotection of F leads to the intermediates B.
Obviously, compounds with inverted ether and thioether linkers can be prepared by similar reaction sequences, inverting substituent-patterns on the aromatic moieties. 
Another method to prepare compounds of the type D or I-B involves cross-coupling reactions of arylstannanes (Lam et al., Tetrahedron Lett. 2002, 43, 3091), arylboronates (Lam et al., Synlett 2000, 5, 674); Chan et al., Tetrahedron Lett. 1998, 39, 2933) or aryl halides (Buchwald et al., J. Amer. Chem. Soc. 1996, 118, 7215) with the corresponding amines or amides (scheme 3). 
Once again, compounds with inverted ether and thioether linkers can be prepared by similar reaction sequences, inverting substituent-patterns on the aromatic moieties.
A possibility to prepare compounds I where X is xe2x80x94CH2CH2xe2x80x94 or xe2x80x94CHxe2x95x90CHxe2x80x94 is shown in scheme 4. Wittig- or Wittig-Horner reactions between phosphor-ylides and aromatic aldehydes under standard conditions leads to styrene-derivatives G. These intermediates can be reduced to intermediates H or J Usually, reduction of G by Bechamp-type conditions leads to compounds H, which can then be further reduced to compounds J by catalytic hydrogenation. Using harsher hydrogenation conditions, compounds G can be reduced in one step to give compound J. Compounds H or J are then further processed by the methods depicted in scheme 1 to yield the final products I. Another method to prepare compounds of the type G involves nitration of styrene-derivatives. 
The compounds of the invention are, as already mentioned above, monoamine oxidase B inhibitors and can be used for the treatment or prevention of diseases in which MAO-B inhibitors might be beneficial. These include acute and chronic neurological disorders, cognitive disorders and memory deficits. Treatable neurological disorders are for instance traumatic or chronic degenerative processes of the nervous system, such as Alzheimer""s disease, other types of dementia, minimal cognitive impairment or Parkinson""s disease. Other indications include psychiatric diseases such as depression, anxiety, panic attack, social phobia, schizophrenia, eating and metabolic disorders such as obesity as well as the prevention and treatment of withdrawal syndromes induced by abuse of alcohol, nicotine and other addictive drugs. Other treatable indications may be reward deficiency syndrome (G. M. Sullivan, International patent application No. WO 01/34172 A2), peripheral neuropathy caused by cancer chemotherapy (G. Bobotas, International Patent Application No. WO 97/33572 A1), or the treatment of multiple sclerosis (R. Y. Harris, International patent application No. WO 96/40095 A1) and other neuroinflammatory diseases.
The compounds of the invention are especially useful for the treatment and prevention of Alzheimer""s disease and senile dementia.
The pharmacological activity of the compounds was tested using the following method:
The cDNA""s encoding human MAO-A and MAO-B were transiently transfected into EBNA cells using the procedure described by E.-J. Schlaeger and K. Christensen (Transient Gene Expression in Mammalian Cells Grown in Serum-free Suspension Culture; Cytotechnology, 15: 1-13, 1998). After transfection, cells were homogenised by means of a Polytron homogenizer in 20 mM Tris HCl buffer, pH 8.0, containing 0.5 mM EGTA and 0.5 mM phenylmethanesulfonyl fluoride. Cell membranes were obtained by centrifugation at 45,000xc3x97g and, after two rinsing step with 20 mM Tris HCl buffer, pH 8.0, containing 0.5 mM EGTA, membranes were eventually re-suspended in the above buffer and aliquots stored at xe2x88x9280xc2x0 C. until use.
MAO-A and MAO-B enzymatic activity was assayed in 96-well-plates using a spectrophotometric assay adapted from the method described by M. Zhou and N. Panchuk-Voloshina (A One-Step Fluorometric Method for the Continuous Measurement of Monoamine Oxidase Activity, Analytical Biochemistry, 253: 169-174, 1997). Briefly, membrane aliquots were incubated in 0.1 M potassium phosphate buffer, pH 7.4, for 30 min at 37xc2x0 C. with or without various concentrations of the compounds. After this period, the enzymatic reaction was started by the addition of the MAO substrate tyramine together with 1 U/ml horse-radish peroxidase (Roche Biochemicals) and 80 xcexcM N-acetyl-3,7,-dihydroxyphenoxazine (Amplex Red, Molecular Probes). The samples were further incubated for 30 min at 37xc2x0 C. in a final volume of 200 xcexcl and absorbance was then determined at a wavelength of 570 nm using a SpectraMax plate reader (Molecular Devices). Background (non-specific) absorbance was determined in the presence of 10 xcexcM clorgyline for MAO-A or 10 xcexcM L-deprenyl for MAO-B.
IC50 value were determined from inhibition curves obtained using nine inhibitor concentrations in duplicate, by fitting data to a four parameter logistic equation using a computer program.
The compounds of the present invention are specific MAO-B inhibitors. The IC50 values of preferred compounds of the invention as measured in the assay described above are in the range of 1000 nM or less, typically 100 nM or less, and ideally 50 nM or less.
In the table below are disclosed some IC50 values (nM) of preferred compounds.
The compounds of the invention can be formulated into pharmaceutical compositions. The pharmaceutical compositions can be administered orally, e.g. in the form of tablets, coated tablets, dragxc3xa9es, hard and soft gelatine capsules, solutions, emulsions or suspensions. The pharmaceutical compositions also can be administered rectally, e.g. in the form of suppositories, or parenterally, e.g. in the form of injection solutions.
The compounds of the invention can be processed with pharmaceutically acceptable carriers, e.g. inert, inorganic or organic carriers, such as those generally used in the formulation of pharmaceutical compositions. Such pharmaceutically acceptable carriers are provided, for example, in Remington: The Science and Practice of Pharmacy (Mack Publishing, 1995). Lactose, corn starch or derivatives thereof, talc, stearic acid or its salts and the like can be used, for example, as such carriers for tablets, coated tablets, dragxc3xa9es and hard gelatine capsules.
Suitable carriers for soft gelatine capsules are, for example, vegetable oils, waxes, fats, semi-solid and liquid polyols and the like; depending on the nature of the active substance no carriers are, however, usually required in the case of soft gelatine capsules
Suitable carriers for the production of solutions and syrups are, for example, water, polyols, sucrose, invert sugar, glucose and the like. Adjuvants, such as alcohols, polyols, glycerol, vegetable oils and the like, can be used for aqueous injection solutions of water-soluble salts of the compounds of the invention, but as a rule are not necessary. Suitable carriers for suppositories are, for example, natural or hardened oils, waxes, fats, semi-liquid or liquid polyols and the like.
In addition, the pharmaceutical compositions can contain preservatives, solubilizers, stabilizers, wetting agents, emulsifiers, sweeteners, colorants, flavorants, salts for varying the osmotic pressure, buffers, masking agents or antioxidants. They may also contain other therapeutically valuable substances.
Compounds of the present invention are selective MAO-B inhibitors. Thus, in another embodiment, the present invention provides for methods of treating diseases that are mediated by monoamine oxidase B. Such methods include administering a therapeutically effective amount of a compound of the invention, for example, a compound of formula I or a pharmaceutically acceptable salt thereof, to a patient in need of such treatment. In a preferred embodiment, the invention provides a method for the treatment of Alzheimer""s diease. In another preferred embodiment, the present invention provides a method for the treatment of senile demenita.
The dosage at which a compound of the invention is administered can vary within wide limits and will, of course, be fitted to the individual requirements in each particular case. In general, the effective dosage for oral or parenteral administration is between 0.01-20 mg/kg/day, with a dosage of 0.1-10 mg/kg/day being preferred for all of the indications described. The daily dosage for an adult human being weighing 70 kg accordingly lies between 0.7-1400 mg per day, preferably between 7 and 700 mg per day.
The following examples are provided for illustration of the invention. They should not be considered as limiting the scope of the invention, but merely as being representative thereof. Unless otherwise indicated, the following examples have been performed, regardless of the tense in which they are written.